Search

Exclusive rare Higgs decays into lepton pair plus one light hadron, such as $h\to \rho^0(\omega)\ell\bar{\ell}$, $h\to \pi^0\ell\bar{\ell}$, $h\to \pi^+ (K^+)\ell^-\bar{\nu}_\ell$, and $h\to \rho^+(K^{*+})\ell^-\bar{\nu}_\ell$, have been explored in the standard model. Decay amplitudes are dominantly from the Higgs couplings to gauge bosons and to charged leptons, and their branching ratios are predicted in the range of $10^{-8}\sim 10^{-5}$. We have also analyzed the differential dilepton invariant mass and angular distributions of $h\to \rho^0 \ell^+\ell^-$ decays. It will be challenging to search for these rare processes. Nevertheless, experimental studies of them, in particular, $h\to \rho^0\ell^+\ell^-$ with $\ell=e,\mu$, might be interesting both to help deepen our understanding of the standard model and to probe new physics beyond the standard model in the future high-precision experiments., Comment: 12 pages, 4 figures

We study the long-distance contribution to ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ decay, which is generated by the two-photon intermediate state via the ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\gamma}}^{*}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ transition. It is found that the dispersive two-photon amplitude can interfere with the dominant short-distance amplitude, which gives rise to new theoretical uncertainty in the branching ratio of ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. Our analysis shows that, by taking into account present experimental constraints, this uncertainty could be up to the same order of magnitude as some theoretical uncertainties of $\mathcal{B}({B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ given in the past literature. Future precise studies of the double radiative ${B}_{s}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ decay, both experimentally and theoretically, may help to reduce the uncertainty. This novel effect has never been examined in ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ decay.

A search for the invisible decays of $\omega$ and $\phi$ mesons in $J/\psi\to \omega (\phi)\eta$ transitions has been performed by the BESIII Collaboration very recently. Inspired by this experimental study, we compute the lowest order contribution to branching ratios of ${\cal B}(V\to\bar{\nu}\nu)$ with $V$ denoting $\rho,\;\omega,\;\phi$, as the standard model background to these invisible decays. Our predictions are far below the upper bounds given by the BESIII experiment. We also analyze the $J/\psi\to \eta(\eta^\prime)\bar{\nu}\nu$ processes, and estimate their decay rates. Furthermore, the invisible decays of light pseudoscalar mesons $P$ including $\pi^0$, $\eta$, and $\eta^\prime$ are reexamined in the present note. It is shown that, due to the helicity suppression of the two-neutrino final state, the standard model contributions to $P\to{\rm invisible}$ decays are dominated by $P\to\bar{\nu}\nu \bar{\nu}\nu$ processes., Comment: 8 pages, 4 figures, minor changes and references added. To appear in PRD

Rare weak decays of ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}K\ensuremath{\pi}$ have been investigated in the framework of the $U(3)$ chiral perturbation theory at the leading order. Our study shows that the branching ratio $\mathcal{B}({\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}K\ensuremath{\pi})$ is of the order of ${10}^{\ensuremath{-}11}$, which is far below the present experimental upper bound given by the BESIII Collaboration. By further analysis of ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\pi}}^{0}$, the ratio of isospin amplitudes is found, $|{A}_{1/2}/{A}_{3/2}|\ensuremath{\simeq}35$, which supports that the $\mathrm{\ensuremath{\Delta}}I=1/2$ transition enhancement, namely, the $\mathrm{\ensuremath{\Delta}}I=1/2$ rule, could be functional in ${\ensuremath{\eta}}^{\ensuremath{'}}$ weak decays.

Motivated by some new experimental data, we carry out a phenomenological analysis of D→KπD→Kπ decays including both Cabibbo favored and doubly Cabibbo suppressed modes. Two asymmetries, R(D0)R(D0) and R(D+)R(D+), which are generated through interference between Cabibbo favored and doubly Cabibbo suppressed D→KπD→Kπ transitions, are predicted. The relative strong phase, δKπδKπ, between D0→K−π+D0→K−π+ and D0→K+π−D0→K+π− decays, is estimated. The theoretical results agree well with the current measurements.

We study the decay K^+ -> pi^+ pi^0 e^+ e^-, currently under analysis by the NA62 Collaboration at CERN. In particular, we provide a detailed analysis of the Dalitz plot for the long-distance, gamma^*-mediated, contributions (Bremsstrahlung, direct emission and its interference). We also examine a set of asymmetries to isolate genuine short-distance effects. While we show that charge asymmetries are not required to test short distances, they provide the best environment for its detection. This constitutes by itself a strong motivation for NA62 to study K^- decays in the future. We therefore provide a detailed study of different charge asymmetries and the corresponding estimated signals. Whenever possible, we make contact with the related processes K^+ -> pi^+ pi^0 gamma and K_L -> pi^+ pi^- e^+ e^- and discuss the advantages of K^+ -> pi^+ pi^0 e^+ e^- over them., Comment: 25 pages, 6 figures

We study the CP-violating asymmetry [Formula: see text], which arises, in η → π+π-e+e-, from the angular correlation of the e+e- and π+ π- planes due to the interference between the magnetic and electric decay amplitudes. With the phenomenologically determined magnetic amplitude and branching ratio as input, the asymmetry, induced by the electric bremsstrahlung amplitude through the CP-violating decay η → π+π-, and by an unconventional tensor type operator, has been estimated respectively. The upper bound of [Formula: see text] from the former is about 10-3, and the asymmetry from the latter might be up to O(10-2). One can therefore expect that this CP asymmetry would be an interesting CP-violating observable for the future precise measurements in the η factories.

A systematic method developed by us to evaluate the one-loop electromagnetic self-energies of the low-lying mesons is extended to the case of the ρ-meson. The theoretical prediction of ρ0-ρ± electromagnetic mass splitting is about 0.62 MeV, which is in agreement with the measurements.

A phenomenological analysis of $D\to K\pi$ and $D_s^+\to K K $decays including both Cabibbo-favored and doubly-Cabibbo-suppressed modes have been presented by employing the present experimental data. SU(3) symmetry breaking effects from the decay constants and form factors have been taken into account in the analysis. Three asymmetries, $R(D^0)$, $R(D^+)$, and $R(D_s^+)$, which are generated through interference between Cabbibo-favored and doubly- Cabibbo-suppressed decays, are estimated. Theoretical results agree well with the current measurements., Comment: 9 pages, 1 figure. Some discussions on asymmetries added in Section 3. To appear in Phys. Rev. D

Motivated by the experimental study of $J/\psi\to\gamma ~+$ invisible decay by the CLEO Collaboration, we analyze the process $J/\psi\to \gamma \nu\bar{\nu}$, as the standard model background for this invisible decay, at the lowest order. Our investigation shows that Br($J/\psi\to \gamma \nu\bar{\nu}$) is far below the present experimental upper limit on the branching ratio of $J/\psi\to\gamma ~+$ invisible, which indicates that some interesting room for new physics in this channel might be expected. We also present a similar analysis of the $\eta_c\to \gamma \nu\bar{\nu}$ decay.

Rare decays h → Z V with V denoting the narrow c c ¯ or b b ¯ resonances, such as J / Ψ or ϒ states, have been analyzed. Within the standard model, these channels may proceed through the tree-level transition h → Z Z ⁎ with the virtual Z ⁎ → V , and also loop-induced process h → Z γ ⁎ , followed by γ ⁎ → V . Our analysis shows that, for the bottomonium final states, the decay rate of h → Z ϒ from the loop-induced process is small and the former transition gives the dominant contribution; while, for the charmonium final states, Γ ( h → Z J / Ψ ) and Γ ( h → Z Ψ ( 2 S ) ) induced by h → Z γ ⁎ → Z V could be comparable to the contribution given by the tree-level h → Z Z ⁎ → Z V transition.

By employing vector meson dominance to establish the electromagnetic interactions of hadrons, the electromagnetic self-energy of the neutral pions, which receives the contributions from the vector resonances due to chiral anomaly, is evaluated. This part of the electromagentic mass, which can contribute to the mass difference of $\pi^\pm-\pi^0$, is finite and as expected, is smaller than the contributions due to isospin symmetry breaking and electromagnetic chiral logs corrections, however, could be compared with the contribution from the short distance QCD., Comment: Revtex, 8 pages, no figures

In this paper, U(3)$_L\times$ U(3)$_R$ chiral theory of mesons is extended to the leading order in quark mass expansion in order to evaluate the $\rho^0-\omega$ mixing. It is shown that the use of path integral method to integrate out the quark fields naturally leads to the $\rho^0-\omega$ mixing vertices, and this mixing is entirely from the quark loop in this theory. The off-shell behaviour of the mixing amplitude is analyzed. The on-shell mixing amplitude is obtained from the decay $\omega\to \pi^+\pi^-$. Furthermore, the constraints on the light quark mass parameters are extracted from the $\rho^0-\omega$ mixing and the mesons masses, and the mass splitting of $K^*(892)$-mesons is predicted.

Using the Higgs boson mass ${m}_{h}=125\text{ }\text{ }\mathrm{GeV}$, the radiative Higgs decays $h\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\nu}}_{l}{\overline{\ensuremath{\nu}}}_{l}$ with ${\ensuremath{\nu}}_{l}={\ensuremath{\nu}}_{e}$, ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, and ${\ensuremath{\nu}}_{\ensuremath{\tau}}$ are analyzed in the standard model. Our calculation shows that the inclusive width of these processes, i.e., the sum of $\mathrm{\ensuremath{\Gamma}}(h\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\nu}}_{l}{\overline{\ensuremath{\nu}}}_{l})$ for ${\ensuremath{\nu}}_{l}={\ensuremath{\nu}}_{e}$, ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, ${\ensuremath{\nu}}_{\ensuremath{\tau}}$, is 1.41 keV, which is about 15% of $\mathrm{\ensuremath{\Gamma}}(h\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})$. Therefore, the observation of these channels in future precise experiments may provide some useful information on the Higgs physics in both the standard model and its possible extensions.

There exist certain intrinsic relations between the ultraviolet divergent graphs and the convergent ones at the same loop order in renormalizable quantum field theories. Whereupon we may establish a new method, the intrinsic regularization method, to regularize those divergent graphs. In this paper, we apply this method of QCD at the one-loop order, It turns out to be satisfactory: The gauge invariance is preserved manifestly and the results are the same as those derived by means of other regularization methods.

To one-loop order and $O({\ensuremath{\alpha}}_{\mathrm{EM}}),$ the electromagnetic mass splittings of \ensuremath{\pi}, ${a}_{1},$ $K,$ ${K}_{1}(1400),$ and ${K}^{*}(892)$ are calculated in the framework of $\mathrm{U}{(3)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}{(3)}_{R}$ chiral field theory. The logarithmic divergences emerging in the Feynman integrations of the mesonic loops are factorized by using an intrinsic parameter $g$ of this theory. No other additional parameters or counterterms are introduced to absorb the mesonic loop divergences. When ${f}_{\ensuremath{\pi}},$ ${m}_{\ensuremath{\rho}},$ and ${m}_{a}$ are taken as inputs, the parameter $g$ will be determined and all the physical results are finite and fixed. Dashen's theorem is satisfied in the chiral SU(3) limit of this theory and a rather large violation of the theorem is revealed at the order of ${m}_{s}$ or ${m}_{K}^{2}.$ Mass ratios of light quarks have been determined. A relation for electromagnetic corrections to masses of axial-vector mesons is obtained. It could be regarded as a generalization of Dashen's theorem. Comparing with data, it is found that the nonelectromagnetic mass difference of ${K}^{*}$ is in agreement with the estimation of Schechter, Subbaraman, and Weigel.

The radiative Higgs decays h → γl + l − with l = e, μ and τ are analyzed in the standard model using m h = 125GeV. Both tree and one-loop diagrams for the processes are evaluated. In addition to their decay rates and dilepton invariant mass distributions, we focus on the forward-back asymmetries in these modes. Our calculation shows that the forward-backward asymmetries in h → γe + e − and h → γμ + μ − could be up to 10−2 while in the τ + τ − final state, these asymmetries are below 1%. Thus the forwardbackward asymmetries in h → γl + l − might be interesting observables in the future precise experiments both to test our understanding of Higgs physics in the standard model and to probe the novel Higgs dynamics in new physics scenarios.

Based on experimental data by the Belle Collaboration, we present a phenomenological analysis of the angular distributions in ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ decay. Our study shows that the angular analysis could lead to some interesting observables, and the future experimental investigation of these observables might be very helpful in revealing the nature of the scalar components of the decay. New physics contributions from the two-Higgs-doublet model to this decay have also been examined.

A regularization method named the intrinsic loop regularization is proposed by WANG and GUO. Here, we apply it to the quantum electrodynamics, we find this method can remain gauge invariance very well.

Current experiments do not support, as ATLAS and CMS collaborations at the Large Hadron Collider reported, that the Higgs-like resonance discovered in July 2012 is a pure CP-odd state. We examine a general $hZZ$ vertex which contains CP-even and CP-odd couplings, by studying the process $h\to ZZ^*\to l_1^+l_1^-l_2^+l_2^-$ with $l_1,\, l_2= e$ or $\mu$, to explore the CP mixed property of the Higgs-like particle. One momentum asymmetry and two angular asymmetries have been analyzed in order to reveal the difference from different CP-couplings. Our study shows that these asymmetries could be interesting observables in the future precise experiments., Comment: 13 pages, 6 figures, references and some discussion added

L. Cappiello1,2, O. Cata3, G. D’Ambrosio2,a, Dao-Neng Gao4 Dipartimento di Scienze Fisiche, Universita di Napoli “Federico II”, Via Cintia, 80126 Naples, Italy INFN-Sezione di Napoli, Via Cintia, 80126 Naples, Italy Fakultat fur Physik, Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universitat Munchen, 80333 Munich, Germany Interdisciplinary Center for Theoretical Study and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, China

Belle Collaboration reported a new observed value of K*-(892) mass by studying tau --> K_S pi nu_tau decay, which is significantly different from the current world average value given by Particle Data Group 2006. Motivated by this new data, we revisit the issue on the K*0(892)-K*+(892) mass splitting. Our theoretical estimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues., 5 pages, minor changes, references added

We study possible scalar type interactions in tau^- -->pi^- pi^0 nu_tau decay. One finds that an angular distribution asymmetry, A(s), can be induced from the interference between the scalar part and vector part amplitudes in this decay. Our analysis shows that, in the two-Higgs-doublet model of type II with large tan beta, the charged Higgs contribution could make A(s) up to 10^{-3} without conflict with present experimental constraints. Thus in the future precise experiments in tau-charm factories, this angular distribution asymmetry may be an interesting observable either to be helpful in searching for the signal of the charged Higgs boson or to impose the significant bound on it.

Motivated by some new experimental and theoretical efforts, we update the theoretical analysis of the electron-positron energy asymmetry, which arises, in K_L --> pi0 e+ e-, from the two-photon intermediate state in the standard model. It is found that the measurement of this asymmetry in future experiments may increase our understanding of the K_{L, S} --> pi0 e+ e- decays, which would thus provide some useful information on quark flavor physics. Meanwhile, in the standard model the electron-positron energy asymmetry in the decay of K_S --> pi0 e+ e- is expected to be vanishingly small, therefore the asymmetry in K_S --> pi0 e+ e- might be a very interesting quantity to explore new physics scenarios., Comment: 11 pages, 4 figures. Two figures added to show the sensitivity of the asymmetry to a_S and a_V, and some discussions added. To appear in Phys. Lett. B

The long-distance contribution via the two-photon intermediate state to the forward-backward asymmetries in decays K+ --> pi+ l+ l- (l=e and mu) has been studied within the standard model. In order to evaluate the dispersive part of the K+ --> pi+ gamma* gamma* --> pi+ l+ l- amplitude, we employ a phenomenological form factor to soften the ultraviolet behavior of the transition. It is found that, this long-distance transition, although subject to some theoretical uncertainties, can lead to significant contributions to the forward-backward asymmetries, which could be tested in the future high-precise experiments., Comment: 13 pages, 5 figures

The CP-violating charge asymmetry in decays K+- --> \pi+- \gamma\gamma, which is induced by the electromagnetic penguin operators, has been studied both in thestandard model and in its extensions. Because of a large enhancement of the Wilson coefficients of the electromagnetic penguin operators in the supersymmetric extensions of the standard model, a significant upper bound on this charge asymmetry could be expected, and thus high precision measurements of this interesting CP-violating quantity might explore new physics effects beyond the standard model.

The decay [Formula: see text] is investigated beyond the standard model. Interestingly, the upper limit of the CP-conserving and CP-violating branching ratios of the decay, induced from the possible extensions of the standard model, would be larger than the corresponding branching ratios given in the standard model respectively, and it is expected that the CP-violating part could be enhanced.

Supersymmetric extensions of the Standard Model predict a large enhancement of the Wilson coefficients of the dimension-five electromagnetic penguin operators affecting the direct CP violation in K_L --> pi^0 e^+ e^- and the charge asymmetry in K^\pm --> pi^\pm l^+ l^-. Here we compute the relevant matrix elements in the chiral quark model and compare these with the ones given by lattice calculations, Comment: 12 pages, JHEP style, gluonic corrections to B_T added

We revisit the calculation of the long-distance contribution to the muon-polarization asymmetry LR ,w hich arises, inK + ! ++ , from the two-photon intermediate state. The parity-violating amplitude of this process, induced by the local anomalous K + transition, is analysed; unfortunately, one cannot expect to predict its contribution to the asymmetry by using chiral perturbation theory alone. Here we evaluate this amplitude and its contribution to LR by employing a phenomenological model called the FMV model, in which the utility of the vector and axial-vector resonances exchange is important to soften the ultraviolet behaviour of the transition. We nd that the long-distance contribution is of the same order of magnitude as the standard model short-distance contribution.

Motivated by diquark exchange, we construct a class of extensions of the standard model. These models can generate large CP conserving and CP violating contributions to the doubly Cabbibo suppressed decays D^0\to K^+\pi^- without affecting D^0-\overline{D^0} mixing, contrary to what is usually believed in the literature. We find an interesting specific realization of these models, which has the LR chiral structure and can induce novel density \times density operators. It is new for non-leptonic kaon decays, and particularly, may provide a possible solution to the \Delta I=1/2 rule and direct CP violation, without inducing large flavour changing neutral currents., Comment: LaTeX, 12 pages and 2 eps figures. Minor changes, paper accepted by Physics Letters B

In the framework of $\mathrm{U}(3{)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(3{)}_{R}$ chiral theory of mesons, $\ensuremath{\pi}K$ elastic scattering is studied. The s-wave and p-wave scattering lengths ${(a}_{0}^{3/2}, {a}_{0}^{1/2}, {a}_{1}^{3/2},$ and ${a}_{1}^{1/2})$ and phase shifts $({\ensuremath{\delta}}_{0}^{3/2}, {\ensuremath{\delta}}_{0}^{1/2}, {\ensuremath{\delta}}_{1}^{3/2},$ and ${\ensuremath{\delta}}_{1}^{1/2}),$ the total elastic scattering cross section ${\ensuremath{\sigma}}_{\mathrm{tot}}({\ensuremath{\pi}}^{+}{K}^{+})$ and ${\ensuremath{\sigma}}_{\mathrm{tot}}({\ensuremath{\pi}}^{\ensuremath{-}}{K}^{+}),$ and the p-wave cross section ${\ensuremath{\sigma}}_{p}({\ensuremath{\pi}}^{\ensuremath{-}}{K}^{+})$ are calculated. Theoretical results are in agreement with the experimental data. There is no new parameter in this study.

We study a new contribution, which is a tree-level transition from long-distance dynamics, to K+→π+ℓ+ℓ- (ℓ = e, μ) decays. It is found that this tree-diagram can be calculated unambiguously and would generate the additional contribution to the vector, axial-vector, scalar and pseudoscalar form factor of the decay. Our analysis shows that these form factors are strongly suppressed and this long-distance contribution is well under control.

We discuss how the combined analysis of $B\to K\nu\bar\nu$ and $B\to Kl^+l^-$ can provide us with new physics tests practically free of form factor uncertainties. Residual theory errors are at the level of several percent. This study underlines the excellent motivation for measuring these modes at a Super Flavour Factory, or, in the case of $B\to Kl^+l^-$, also at a hadron collider.

A phenomenological analysis of K???? (KL??+??? and K+??+?0?) with the direct emission photon is carried out beyond the leading order in the chiral perturbation theory. We show that the experimental evidence for the large photon energy dependence of the magnetic amplitude in KL??+??? seems to indicate an interesting consequence: vector meson dominance must be implemented at O(p4), which is not a general feature of the chiral perturbation theory. The phenomenology of K+??+?0? is also analyzed using the same scheme.